Microwaves are cooking appliances to heat food using the nature of electromagnetic waves called micro waves. The microwave heats food by producing heat from inside the food according to a dielectric heating method.
When an electromagnetic wave with a high frequency collides with food, water molecules inside the food are spinning and accordingly, molecular arrangement of the food becomes in disorder. The microwave heats food using heat produced when the water molecules are spinning.
In general, it is hard to see into the cooking room of the microwave during cooking, so one has to open the door and check the cooking process to know of the detailed cooking process.